NEW YORK (CNN) -- Two former New York Police Department detectives were sentenced to life in prison without parole Friday for operating as Mafia hit men while employed by the NYPD.

Louis Eppolito, 60, and Stephen Caracappa, 67, who spent a combined 44 years on the force and once worked as partners, were found guilty in April 2006 of engaging in racketeering.

According to prosecutors, they were paid $4,000 a month by the Mafia and were personally paid $65,000 by Luchese crime family underboss Anthony "Gaspipe" Casso for killing another mobster during a phony traffic stop. Authorities said Casso regarded the officers as his "crystal ball," likely referring to their alleged involvement in relaying classified information to the Luchese family.

Eppolito and Caracappa, who reiterated their innocence at Friday's sentencing, were found guilty of participating in or aiding eight murders, two attempted murders and one murder conspiracy, as well as witness tampering, witness retaliation, obstruction of justice, money laundering and drug charges.

Eppolito was sentenced to life in prison plus 100 years, while Caracappa received life in prison plus 80 years. They were also fined a combined $4 million.

"The sentences imposed today bring some measure of closure for the families of the victims of these defendants' unspeakable crimes and for the citizens of the city whose trust these men betrayed," U.S. Attorney Benton J. Campbell said in a news release. "We are gratified that the defendants will spend the rest of their lives behind bars."

Eppolito, who grew up in a Mafia family, wrote the book "Mafia Cop," in which he described how he turned away from the "family business" to become what he said was one of the police department's most decorated officers. He also had small roles in several films, including the role of Fat Andy in the 1990 mob film "Goodfellas."

Caracappa was a member of the NYPD's Organized Crime Homicide Unit, which he helped create.